It is known that an internal combustion engine of a motor vehicle typically includes an oil system suitable for lubricating the rotating or sliding components of the engine. The oil system generally has an oil pump driven by the engine, which draws lubricating oil from a sump and delivers it under pressure through a main oil gallery of the engine cylinder block. The main oil gallery is connected via respective pipes to a plurality of exit holes for lubricating crankshaft bearings (main bearings and big-end bearings), camshaft bearings operating the valves, tappets, and the like.
In order to cool and lubricate the engine pistons and the related cylinders, the oil system further includes a plurality of jet nozzles individually provided for squirting oil into an upper crankcase area towards the engine pistons. Each jet nozzle is usually equipped with a check valve that automatically opens the jet nozzle only if the oil pressure exceeds a predetermined threshold value thereof.
In modern internal combustion engines, the jet nozzles can be connected to a common auxiliary oil gallery, also referred as an Oil Pistons Cooling Jets (OPCJ) gallery. The OPCJ gallery is realized in the cylinder block of the internal combustion engine and communicates with the main oil gallery through an electrically driven valve, conventionally referred as a squirters valve or an Oil Piston Cooling Jets (OPCJ) valve.
This OPCJ valve is generally controlled by an engine control unit (ECU) according to a managing strategy contrived for allowing an effective cooling of the pistons and consequently a significant fuel saving and polluting emission reduction. This managing strategy is usually performed with the aid of a wide range pressure sensor located in the main oil gallery, namely a sensor capable to sense the actual value of the pressure over a wide range of values.
At least one object herein is to provide a method to diagnose a fault of the OPCJ valve, namely whether the OPCJ valve effectively opens and closes the communication between the main gallery and the auxiliary gallery in response of the commands delivered by the ECU. Another object is to provide a simple and rational method, which implies cheaper hardware requirements than the known method. In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.